Fibroblast growth factor 8 (FGF8) is a signaling protein with critical functions during normal embryogenesis and tissue homeostasis; abnormal FGF signaling causes human birth defects and dysregulated FGF8 production, which contributes to pathogenesis of numerous cancers. In spite of the importance of this protein in vertebrate gastrulation, left-right asymmetry, craniofacial, limb, renal, cardiovascular, as well as central nervous system development, fundamental questions about the molecular biology of this protein in vivo remain unanswered due to the lack of sufficiently sensitive anti-FGF8 antibodies. The principal investigator and many others in the field have tested and attempted to optimize commercially generated antibodies and also generated custom antibodies; in spite of the efforts of many laboratories with significant expertise in immunohistochemistry, the antibodies are insufficiently sensitive and have prohibitively high background for developmental studies. Genetic labeling strategies are the best available choices at present, however, she and others have found that the required alterations to the Fgf8 locus to generate reporter alleles can disrupt normal transcriptional regulation, and it may also interfere with translational regulatory mechanisms. Moreover, such strategies do not allow one to assess endogenous protein location and function. The goal of this application is to develop high affinity, FGF8-specific, labeled aptamers which will subsequently allow the principal investigator and others to address important outstanding questions about the localization, signaling capacity and range, receptor interactions, as well as tissue-specific production and processing of different FGF8 protein isoforms during mouse embryonic development in vivo. In the future, these aptamers can be employed in studies investigating mechanisms of carcinogenesis and may be tested for therapeutic properties. PROJECT NARRATIVE: Fibroblast growth factor 8 (FGF8) is a signaling protein with critical functions during normal embryogenesis and tissue homeostasis; abnormal FGF signaling causes human birth defects, and dysregulated FGF8 production contributes to pathogenesis of numerous cancers. In spite of the importance of this protein in vertebrate gastrulation, left-right asymmetry, craniofacial, limb, renal, cardiovascular, as well as central nervous system development, fundamental questions about the molecular biology of this protein in vivo remain unanswered due to the lack of sufficiently sensitive anti-FGF8 antibodies. The goal of this application is to develop high affinity, FGF8-specific, labeled aptamers which will subsequently allow the investigator and others to address important outstanding questions about the localization, signaling capacity and range, receptor interactions, and tissue-specific production as well as processing of different FGF8 protein isoforms during mouse embryonic development in vivo. In the future, these aptamers can be employed in studies investigating mechanisms of carcinogenesis and may be tested for therapeutic properties.